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A new form of NaMnAsO₄.

ABSTRACT: A new form of NaMnAsO₄, sodium manganese(II) orthoarsenate, has been obtained under hydro-thermal conditions, and is referred to as the ?-polymorph. In contrast to the previously reported ortho-rhom-bic ?-polymorph that crystallizes in the olivine-type of structure and has one manganese(II) cation in a distorted octa-hedral coordination, the current ?-polymorph contains two manganese(II) cations in [5]-coordination, inter-mediate between a square-pyramid and a trigonal bipyramid. In the crystal structure of ?-NaMnAsO₄, four [MnO₅] polyhedra are linked through vertex- and edge-sharing into finite {Mn₄O₁₆} units strung into rows parallel to [100]. These units are linked through two distinct orthoarsenate groups into a framework structure with channels propagating parallel to the manganese oxide rows. Both unique sodium cations are situated inside the channels and exhibit coordination numbers of six and seven. ?-NaMnAsO₄ is isotypic with one form of NaCoPO₄ and with NaCuAsO₄.

SUBMITTER: Weil M

PROVIDER: S-EPMC6659317 | biostudies-literature | 2019 Jul

REPOSITORIES: biostudies-literature

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A new form of NaMnAsO4.

Weil Matthias M Veyer Théo T

Acta crystallographica. Section E, Crystallographic communications 20190607 Pt 7

A new form of NaMnAsO4, sodium manganese(II) orthoarsenate, has been obtained under hydro-thermal conditions, and is referred to as the β-polymorph. In contrast to the previously reported ortho-rhom-bic α-polymorph that crystallizes in the olivine-type of structure and has one manganese(II) cation in a distorted octa-hedral coordination, the current β-polymorph contains two manganese(II) cations in [5]-coordination, inter-mediate between a square-pyramid and a trigonal bipyramid. In t ...[more]

PMID: 31392005

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